The present invention relates to an inductive coupler, and more specifically to a separable inductive coupler which is operable by electromagnetic induction to transfer electrical power and is applicable to a system for recharging a battery for electrical powered vehicle, and the like.
There has been known an inductive coupler having a primary coil wound round a primary core and connected to the source of electrical power and a secondary coil wound round a secondary core matable or engageable with the primary counterpart, wherein alternating current applied across the primary winding produces a moving magnetic field which in turn induces a voltage across the secondary winding, thus electrical power being transferred from the primary winding to the secondary winding. The primary and secondary cores may be configured in various shapes, e.g. a channel shape as shown in Publication of unexamined Japanese patent application No. 63-151006 (1988) and coaxial cylindrical shape as described in Publication of unexamined Japanese patent application No. 63-240331 (1988). An E-shaped core is also known which has a central post projecting from the axial center of a disc-shaped base and an annular skirt projecting from the rim of the base in the same direction, thus forming therebetween an annular groove. The E-shaped and coaxial cylindrical shaped cores may also be referred to as "tripod" type due to their three-legged configurations as seen in axial cross section thereof.
In the inductive coupling apparatus having a pair E-shaped primary and secondary cores, each core has a winding disposed in the above annular groove, thus forming a coil assembly, and the two coil assemblies are mated together at the distal or abutment end surfaces of the cores thereby to make a magnetic circuit for transferring electrical power from the primary to the secondary by application of alternating current across the primary winding. For this purposes, either one of the coil assemblies must be brought adjacent to and located properly with respect the other, and then abutted together. When the power transferring has been completed, the above one coil assembly is removed away from the other.
When a higher power is to be transferred by the above inductive coupler, the coil assemblies thereof will inevitably become larger in size and heavier in weight and, therefore, the coil assembly that is carried and moved relative to the other by an operator, e.g. at a battery recharging station, becomes bulky to handle. Frequent operations to install and remove a heavy movable coil assembly with respect to a stationary assembly will apparently require laborious efforts of the operator.
For improvement in the power transferring efficiency of the inductive coupler, i.e. secondary effective power/primary effective power, the cores should be mated at their abutment surfaces with as little core-to-core gap as possible. However, this gap is affected by core vibration caused by application of alternating current across the primary winding of the device. To stabilize the electromagnetic induction of the dived, such vibration should be restricted to minimum